Section (3) fpathconf
Name
fpathconf, pathconf — get configuration values for files
Synopsis
#include <unistd.h>
long
fpathconf( |
int fd, |
int name) ; |
long
pathconf( |
const char *path, |
int name) ; |
DESCRIPTION
fpathconf
() gets a value for
the configuration option name
for the open file
descriptor fd
.
pathconf
() gets a value for
configuration option name
for the filename
path
.
The corresponding macros defined in <
unistd.h
>
are minimum values; if an application wants to take advantage
of values which may change, a call to fpathconf
() or pathconf
() can be made, which may yield
more liberal results.
Setting name
equal
to one of the following constants returns the following
configuration options:
_PC_LINK_MAX
-
The maximum number of links to the file. If
fd
orpath
refer to a directory, then the value applies to the whole directory. The corresponding macro is_POSIX_LINK_MAX
. _PC_MAX_CANON
-
The maximum length of a formatted input line, where
fd
orpath
must refer to a terminal. The corresponding macro is_POSIX_MAX_CANON
. _PC_MAX_INPUT
-
The maximum length of an input line, where
fd
orpath
must refer to a terminal. The corresponding macro is_POSIX_MAX_INPUT
. _PC_NAME_MAX
-
The maximum length of a filename in the directory
path
orfd
that the process is allowed to create. The corresponding macro is_POSIX_NAME_MAX
. _PC_PATH_MAX
-
The maximum length of a relative pathname when
path
orfd
is the current working directory. The corresponding macro is_POSIX_PATH_MAX
. _PC_PIPE_BUF
-
The maximum number of bytes that can be written atomically to a pipe of FIFO. For
fpathconf
(),fd
should refer to a pipe or FIFO. Forfpathconf
(),path
should refer to a FIFO or a directory; in the latter case, the returned value corresponds to FIFOs created in that directory. The corresponding macro is_POSIX_PIPE_BUF
. _PC_CHOWN_RESTRICTED
-
This returns a positive value if the use of chown(2) and fchown(2) for changing a file_zsingle_quotesz_s user ID is restricted to a process with appropriate privileges, and changing a file_zsingle_quotesz_s group ID to a value other than the process_zsingle_quotesz_s effective group ID or one of its supplementary group IDs is restricted to a process with appropriate privileges. According to POSIX.1, this variable shall always be defined with a value other than −1. The corresponding macro is
_POSIX_CHOWN_RESTRICTED
.If
fd
orpath
refers to a directory, then the return value applies to all files in that directory. _PC_NO_TRUNC
-
This returns nonzero if accessing filenames longer than
_POSIX_NAME_MAX
generates an error. The corresponding macro is_POSIX_NO_TRUNC
. _PC_VDISABLE
-
This returns nonzero if special character processing can be disabled, where
fd
orpath
must refer to a terminal.
RETURN VALUE
The return value of these functions is one of the following:
-
On error, −1 is returned and
errno
is set to indicate the cause of the error (for example, EINVAL, indicating thatname
is invalid). -
If
name
corresponds to a maximum or minimum limit, and that limit is indeterminate, −1 is returned anderrno
is not changed. (To distinguish an indeterminate limit from an error, seterrno
to zero before the call, and then check whethererrno
is nonzero when −1 is returned.) -
If
name
corresponds to an option, a positive value is returned if the option is supported, and −1 is returned if the option is not supported. -
Otherwise, the current value of the option or limit is returned. This value will not be more restrictive than the corresponding value that was described to the application in
<
unistd.h
>
or<
limits.h
>
when the application was compiled.
ERRORS
- EACCES
-
(
pathconf
()) Search permission is denied for one of the directories in the path prefix ofpath
. - EBADF
-
(
fpathconf
())fd
is not a valid file descriptor. - EINVAL
-
name
is invalid. - EINVAL
-
The implementation does not support an association of
name
with the specified file. - ELOOP
-
(
pathconf
()) Too many symbolic links were encountered while resolvingpath
. - ENAMETOOLONG
-
(
pathconf
())path
is too long. - ENOENT
-
(
pathconf
()) A component ofpath
does not exist, orpath
is an empty string. - ENOTDIR
-
(
pathconf
()) A component used as a directory inpath
is not in fact a directory.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
fpathconf (), pathconf () |
Thread safety | MT-Safe |
NOTES
Files with name lengths longer than the value returned for
name
equal to
_PC_NAME_MAX
may exist in the
given directory.
Some returned values may be huge; they are not suitable for allocating memory.
COLOPHON
This page is part of release 4.16 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
Copyright (c) 1993 by Thomas Koenig (ig25rz.uni-karlsruhe.de) and Copyright (C) 2017 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified Wed Jul 28 11:12:26 1993 by Rik Faith (faithcs.unc.edu) FIXME Probably all of the following should be documented: _PC_SYNC_IO, _PC_ASYNC_IO, _PC_PRIO_IO, _PC_SOCK_MAXBUF, _PC_FILESIZEBITS, _PC_REC_INCR_XFER_SIZE, _PC_REC_MAX_XFER_SIZE, _PC_REC_MIN_XFER_SIZE, _PC_REC_XFER_ALIGN, _PC_ALLOC_SIZE_MIN, _PC_SYMLINK_MAX, _PC_2_SYMLINKS |